1. Field of the Invention
The present invention relates generally to the field of telephony. More specifically, the present invention discloses a current generator which provides a conventional nominal DC bias current in a telephone loop, and which also temporarily provides a higher "zap" current in cases of high telephone loop resistance.
2. Statement of the Problem
Telephone loop resistances vary widely depending on a number of factors, including the length and condition of the telephone loop. In particular, following initial installation or subsequent repair of a telephone loop, splice resistances may present a substantial problem. Other electrical anomalies may also result from splices and other connections made during installation or repair of a telephone loop. The prior art recognizes that such splice resistances and other anomalies can often be reduced or eliminated by temporarily introducing a relatively high "zap" current into the telephone loop for a few seconds following installation or repair. Ideally, the voltage placed across the telephone loop should be automatically adjusted by the generator to keep the current within the desired range of values.
The portions of the circuitry in the present invention relating to regulation of the nominal DC bias current in the telephone loop, and the longitudinal balance circuitry are conventional. Examples of such circuitry are shown in the following prior art references:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Huft, et al. 4,577,064 Mar. 18, 1986 Huft 4,560,834 Dec. 24, 1985 ______________________________________
3. Solution to the Problem
None of the prior art references disclose a device for generating a "zap" current in which the voltage placed across the telephone loop is automatically increased in a number of predetermined steps if the current actually measured by the device in the telephone loop fails to exceed one or more predetermined minimum values.